Conventionally, in construction equipment, a hydraulic cylinder and other structures are connected to a frame or the like through pin connection. When performing pin connection, particularly in large construction equipment, a spherical slide bearing system is used (JP10-141354).
A spherical slide bearing is equipped with an annular outer bearing, and an inner ring that is also formed in an annular configuration and slidably fitted into the outer ring; a pin is inserted into the inner ring, and is fixed to a frame.
In a large spherical slide bearing system as used in construction equipment, sliding is caused between the outer ring and the inner ring so as to allow rotational motion in an arbitrary direction; further, circumferential sliding is also caused between the inner ring and the pin. This is because there is provided a predetermined gap between the inner ring and the pin to thereby facilitate the insertion of the pin into the inner ring and to achieve an improvement in terms of the ease with which the pin, which is a heavy component, is incorporated.
When sliding is to be effected in two gap portions as between the outer ring and the inner ring and between the inner ring and the pin, it is necessary to supply grease to both of the two gap portions. As a grease supply line, a construction is available in which grease is supplied from the outer side of the outer ring as disclosed in the above-mentioned patent document; apart from this, depending upon the condition under which the spherical bearing is provided, there is also available a construction in which grease is supplied through the interior of the pin.
In the construction in which grease is supplied through the interior of the pin, grease is first discharged from a grease supply flow path providing communication between the interior of the pin and the outer peripheral surface thereof to supply grease to the gap between the pin and the inner ring, from which grease is further guided for supply to the gap between the inner ring and the outer ring through a communication flow path provided in the inner ring, whereby the two gap portions are filled with grease to effect lubrication between the sliding surfaces.
It should be noted, however, that, in the construction in which grease is supplied through the interior of the pin, the gap between the inner and outer rings is larger than the gap between the pin and the inner ring due to the construction. Thus, while at the early stage of grease supply both gaps are uniformly filled with grease, in the subsequent grease supply for supplementing grease, more grease is supplied to the gap involving less flow path resistance, that is, to the larger gap between the inner and outer rings.
When this state is allowed to continue, the amount of grease supplied to the smaller gap between the pin and the inner ring decreases, so that the lubrication of this portion ceases to be effected in a satisfactory manner, and the sliding surfaces are heated to promote a deterioration in the grease. As a result, deteriorated solid grease can be allowed to enter the communication flow path for guiding grease to the gap between the inner and outer rings; this will cause clogging in the communication flow path, thereby making it impossible to effect grease supply to the gap between the inner and outer rings in a satisfactory manner; thus, the bearing as a whole will be heated to cause seizure, resulting in breakage of the inner ring.
It is an object of the present invention to provide a spherical slide bearing system in which it is possible to reliably prevent seizure even in a construction in which grease is supplied through the interior of a pin, thereby achieving an improvement in terms of durability.